JP4686849B2 - Tungsten seal glass for fluorescent lamps - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a tungsten seal glass used for a glass tube of a fluorescent lamp serving as a light source of an illumination device such as a liquid crystal display element.
[0002]
[Prior art]
Liquid crystal display elements are broadly classified into reflective liquid crystal display elements that use natural light and room illumination light, and transmissive liquid crystal display elements that use backlight light, for example, depending on how the light source is used. A transmissive liquid crystal display element using a backlight is mainly used for applications requiring high-quality display such as notebook personal computers, TV monitors, and in-vehicle instruments. Reflective liquid crystal display elements are used for wristwatches and small electronic desk calculators, especially those with low power consumption, but recently these are also used with a front light that is turned on as necessary. Some will do.
[0003]
The light emission principle of a fluorescent lamp that is a light source for a backlight or front light is the same as that of a general lighting fluorescent lamp. Mercury gas, xenon gas, etc. enclosed by discharge between electrodes are excited and emitted from the excited gas. The fluorescent material applied to the inner wall surface of the glass tube emits visible light by ultraviolet rays. However, the major difference from a general fluorescent lamp is that the glass tube has a small diameter and a small thickness. Conventionally, lead glass soda-based soft glass has been used for the glass tube of this fluorescent lamp because of its ease of processing and past achievements as lighting glass, and inexpensive jumet has been used as the introduced metal.
[0004]
However, as the liquid crystal display elements become thinner, lighter, and consume less power, fluorescent lamps are required to be thinner and thinner, but the fluorescent lamps are structurally mechanically thin. The glass tube is required to have higher strength and lower expansion because of a decrease in strength and an increase in heat generation of the lamp. In order to improve the light emission efficiency, the frequency of the lighting circuit has been increased, and accordingly, a glass tube as an insulator is required to have a high volume resistivity and a low dielectric loss. For this reason, the conventional lead soda-based soft glass material cannot satisfy these requirements.
[0005]
Therefore, it has been studied to produce a fluorescent lamp using a borosilicate hard glass, which has higher thermal and mechanical strength than lead soda soft glass and is advantageous in terms of electrical insulation. As a result, conventionally known fluorescent lamps using tungsten seal glass and tungsten metal have been developed and commercialized as a combination of hard glass and metal that can be hermetically sealed.
[0006]
[Problems to be solved by the invention]
However, the glass tube of the above-described fluorescent lamp for backlight uses a borosilicate tungsten seal glass material generally used for a conventional xenon flash lamp as it is, and is simply formed into a thin tube and processed. Therefore, there are the following problems.
[0007]
(1) The glass is discolored (so-called ultraviolet solarization) by ultraviolet rays emitted from excited mercury gas or the like. When the color of the glass changes, the luminance decreases and the emission color shifts, leading to quality deterioration of the liquid crystal display element.
[0008]
(2) Since the glass used for the xenon flash lamp is originally converted, it is designed to transmit a certain amount of ultraviolet rays so as to withstand the flash of the xenon flash lamp. However, in the case of a fluorescent lamp, the transmitted ultraviolet rays discolor and deteriorate other members constituting the backlight and the front light, such as a resin light guide plate and a reflection plate.
[0009]
(3) The devitrification property is very high, the glass is easily devitrified at the time of forming the tube glass, and the glass is easily deteriorated, and it becomes difficult to produce a glass tube having high dimensional accuracy. If a glass tube with poor dimensional accuracy is used, the phosphor cannot be uniformly applied, resulting in uneven brightness. In addition, in an optical system composed of a fluorescent lamp, a light guide plate, and a reflection plate, it cannot be assembled according to the design dimensions, which causes a decrease in luminance or luminance unevenness of the backlight unit or the front light unit itself.
[0010]
(4) The volume resistivity of the glass at 250 ° C. is about 10 ^8.5 Ω · cm, and the electrical insulation is insufficient. In a small-diameter, long, and high-intensity fluorescent lamp, the voltage applied for lighting is high, reaching several hundred volts. However, in the conventional glass that does not have high electrical insulation, leakage occurs and heat is generated, and in the worst case, the glass melts and the lamp function may be completely lost.
[0011]
The present invention has been made in view of the above circumstances, and is excellent in ultraviolet solarization resistance, ultraviolet shielding property, devitrification, and electrical insulation, and is suitable as a tungsten seal as a glass tube for a fluorescent lamp of a backlight or front light. The object is to provide glass.
[0012]
[Means for Solving the Problems]
That is, the tungsten seal glass for a fluorescent lamp of the present invention is, in mass percentage, SiO ₂ 65 to 72.3 %, B ₂ O ₃ 13 to 25%, Al ₂ O ₃ 2 to 6%, MgO + CaO + SrO + BaO + ZnO 0.5 to 5 0.8%, Li ₂ O + Na ₂ O + K ₂ O 3-8%, Fe ₂ O ₃ + CeO ₂ 0.01-4%, Fe ₂ O ₃ 0-0.5 %, TiO ₂ + Sb ₂ O ₃ + PbO 0-10 %, ZrO ₂ 0 to 2%, and Na ₂ O / (Na ₂ O + K ₂ O) ≦ 0.6.
[0013]
[Action]
In the tungsten seal glass for a fluorescent lamp of the present invention, the reason why the content of each component is limited as described above is as follows.
[0014]
SiO ₂ is a main component necessary for constituting the skeleton of the glass, and its content is 65 to 72.3 %, preferably 68 to 72.3 %. When the SiO ₂ is too large, devitrification is rapidly worsening. In addition, it takes time to melt the silica raw material, making it unsuitable for mass production. Furthermore, the coefficient of thermal expansion of the glass becomes too small to be compatible with that of tungsten, making sealing difficult. On the other hand, if it is less than 65%, the chemical durability is deteriorated, so that the glass surface is burned, the transmittance is lowered, and the luminance of the fluorescent lamp is lowered. In addition, the coefficient of thermal expansion of the glass becomes too large to match that of tungsten, making sealing difficult.
[0015]
B ₂ O ₃ is a component necessary for improving meltability, adjusting viscosity, and improving chemical durability, and its content is 13 to 25%, preferably 13 to 19%. When B ₂ O ₃ is more than 25%, there is a problem that evaporation from the glass melt increases and a homogeneous glass cannot be obtained, or the member is evaporated by evaporation during heat processing during the lamp manufacturing process. Moreover, the chemical durability of glass deteriorates. On the other hand, B ₂ O ₃ becomes too high if too little viscosity melt, processing becomes difficult.
[0016]
Al ₂ O ₃ is a component that greatly improves the devitrification of the glass, and its content is 2 to 6%, preferably 2.3 to 4.5%. If the Al ₂ O ₃ content is more than 6%, the viscosity of the glass melt becomes too high, and it becomes impossible to obtain a glass free from bubbles and striae. On the other hand, if it is less than 2%, the above-mentioned effects cannot be obtained, and it becomes difficult to produce homogeneous glass and to form stably.
[0017]
In the present invention, it is preferable to adjust SiO ₂ and Al ₂ O ₃ so that Al ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is in a range of 0.032 to 0.055 by mass ratio. . If this value is 0.032 or more, the liquidus viscosity becomes 10 ⁵ dPa · s or more, devitrification is improved, and stable production at an industrial level becomes easy. However, if it exceeds 0.055, glass melting becomes difficult.
[0018]
MgO, CaO, SrO, BaO and ZnO have the effect of facilitating melting by lowering the viscosity of the glass melt or improving the chemical durability of the glass. 5.8%, preferably 1-4%. When the total amount of these components is more than 5.8%, devitrification and phase separation occur in the glass, and it is impossible to obtain a glass with high homogeneity and transparency. On the other hand, if it is less than 0.5%, the meltability and chemical durability are lowered.
[0019]
Of the above components, BaO is particularly effective in reducing the viscosity, and is less effective in causing devitrification and phase separation in the glass than MgO and CaO. It is desirable to contain 5 to 3%. When BaO is more than 4%, devitrification occurs, and when it is less than 0.1%, the above-described effects cannot be obtained. The contents of MgO, CaO, SrO and ZnO are MgO 0-3% (especially 0-1.5%), CaO 0-3% (especially 0-1.5%), SrO 0-5% ( In particular, 0 to 2%) and ZnO 0 to 5% (particularly 0 to 2%) are preferable. If the content of each component exceeds the above range, devitrification or phase separation occurs, making it difficult to obtain a transparent glass.
[0020]
Li ₂ O is an alkali metal oxide, Na ₂ O, and K ₂ O facilitates melting of the glass, a component added to adjust the thermal expansion coefficient and viscosity, the content is 3 in total -8%, preferably 4-7%. If the total amount of these components is more than 8%, the coefficient of thermal expansion becomes too high, so that it is not suitable for a tungsten seal, and the chemical durability is greatly lowered. On the other hand, if it is less than 3%, vitrification becomes difficult, and the thermal expansion coefficient becomes too small.
[0021]
The content of Li ₂ O, Na ₂ O, and K ₂ O is Li ₂ O 0 to 3% (particularly 0.1 to ₂ %), Na ₂ O 0 to 5% (particularly 0.5 to 3%). K ₂ O is preferably 0.5 to 7% (particularly 1 to 6%). If Li ₂ O exceeds 3%, phase separation tends to occur. When Na ₂ O exceeds 5%, the thermal expansion coefficient becomes too large. Moreover, the weather resistance deteriorates. If K ₂ O exceeds 7%, the thermal expansion coefficient tends to be large, and if it is less than 0.5%, the thermal expansion coefficient is small and vitrification becomes difficult.
[0022]
In the present invention, it is important to adjust Na ₂ O and K ₂ O so that Na ₂ O / (Na ₂ O + K ₂ O) is 0.6 or less in terms of mass ratio. If this value exceeds 0.6, the electrical insulation is insufficient, but if it is 0.6 or less, the volume resistivity at 250 ° C. is 10 ^8.7 Ω · cm or more, and high electrical insulation is obtained. Can do.
[0023]
Fe ₂ O ₃ and CeO ₂ are components that absorb ultraviolet wavelengths and improve ultraviolet shielding properties. Moreover, ultraviolet solarization can be made difficult to occur by increasing the ultraviolet shielding property of the glass. The total content is 0.01 to 4%, preferably 0.015 to 1%. When the total amount of these components exceeds 4%, the absorption of visible light increases, and the brightness and color tone necessary for a fluorescent lamp cannot be obtained. On the other hand, if less than 0.01%, the effect is not obtained.
[0024]
The content of Fe ₂ O ₃ and CeO ₂ is preferably 0 to 0.5% for Fe ₂ O _{3 and} 0 to 4% (particularly 0 to 3%) for CeO ₂ . Incidentally, _Fe 2 _{O 3} tends too colored becomes remarkable, with colored and CeO ₂ exceeds 4%, devitrification is likely to occur. From the viewpoint of raw material cost, it is desirable to use only Fe ₂ O ₃ . In this case, in order to obtain a sufficient ultraviolet shielding effect, it is preferable to contain Fe ₂ O ₃ by 0.01% or more.
[0025]
TiO ₂ , Sb ₂ O ₃ and PbO are all components that impart high ultraviolet solarization resistance to glass, and the total amount is 0 to 10%, preferably 0.05 to 10%, more preferably 0.1. ~ 3%. When the total amount of these components exceeds 10%, devitrification occurs in the glass, or coloring occurs, and a transparent glass free from color shift cannot be obtained.
[0026]
The contents of TiO ₂ , Sb ₂ O ₃ and PbO are TiO ₂ 0-10% (especially 0.1-5%), PbO 0-10% (especially 0-1%), Sb ₂ O ₃ 0-2. % (Particularly 0 to 1%). If TiO ₂ exceeds 10%, the glass itself tends to be colored, and the devitrification property deteriorates rapidly, making it difficult to obtain a transparent and homogeneous glass. On the other hand, if PbO exceeds a predetermined amount, the glass itself is likely to be colored like TiO _2, and it is difficult to obtain a homogeneous glass by evaporating at the time of melting. Furthermore, when Sb ₂ O ₃ exceeds a predetermined amount, it becomes difficult to obtain a homogeneous glass.
[0027]
Further, if PbO or Sb ₂ O ₃ is excessively contained in the glass, the glass is colored brown or black due to thermal processing in the manufacturing process of the fluorescent lamp, which is not preferable. For environmental reasons, it is preferable to use TiO ₂ as much as possible.
[0028]
ZrO ₂ is a component for improving weather resistance, and its content is 0 to 2%, preferably 0 to 1%. When ZrO ₂ exceeds 2%, devitrification deteriorates.
[0029]
In addition to the above components, an appropriate amount of components such as P ₂ O ₅ , SO ₃ , F, and Cl can be added for the purpose of adjusting the viscosity of the glass and improving weather resistance, meltability, clarity, and the like. is there.
[0030]
The tungsten seal glass of the present invention having the above composition has a thermal expansion coefficient of 34 to 43 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 380 ° C., a liquidus viscosity of 10 ⁵ dPa · s or more, and a volume at 250 ° C. ^Its resistivity is 10 ^8.7 Ω · cm or more, and it has properties such as high resistance to ultraviolet solarization and high ultraviolet shielding properties.
[0031]
【Example】
Next, the tungsten seal glass of this invention is demonstrated based on an Example.
[0032]
Tables 1 to 4 show examples of the present invention (sample Nos. 1 to 3 and 5 to 20), and Table 5 shows comparative examples (samples No. 21 and 22). Sample No. 4 is a reference example. The sample No. 21 is a tungsten seal glass used in a conventional fluorescent lamp. This glass was originally developed for xenon flash lamps.
[0033]
[Table 1]
[0034]
[Table 2]
[0035]
[Table 3]
[0036]
[Table 4]
[0037]
[Table 5]
[0038]
No. shown in the table. Each sample of 1-22 was prepared as follows.
[0039]
First, glass materials were prepared so as to have the composition shown in the table, and then melted at 1550 ° C. for 8 hours using a platinum crucible. After melting, the melt was shaped into a predetermined shape and processed to prepare each glass sample.
[0040]
Next, for each sample, the linear expansion coefficient, the difference in spectral transmittance in the visible region before and after ultraviolet irradiation, the spectral transmittance in the ultraviolet region, the temperature and viscosity of the liquidus, and the volume resistivity were measured. The results are shown in Tables 6-10. The liquidus viscosity and volume resistivity are shown as logarithmic values.
[0041]
[Table 6]
[0042]
[Table 7]
[0043]
[Table 8]
[0044]
[Table 9]
[0045]
[Table 10]
[0046]
As is apparent from the table, No. 1 as an example of the present invention. Samples 1 to 3 and 5 to 20 have a linear expansion coefficient of 35.1 to 40.5 × 10 ⁻⁷ / ° C., a decrease in visible light transmittance due to ultraviolet irradiation of 1.8% or less, and an ultraviolet transmittance. Was 1.6% or less, the liquidus viscosity was 10 ⁵ dPa · s or more, and the volume resistivity was 10 ^8.7 Ω · cm or more.
[0047]
On the other hand, a comparative example No. Sample No. 21 has a large decrease in visible light transmittance due to ultraviolet irradiation of 8.5%, a high ultraviolet transmittance of 20%, a low liquidus viscosity of 10 ^4.7 dPa · s, and a volume resistivity. It was as low as 10 ^8.5 Ω · cm. No. In the sample No. 22, the addition of TiO ₂ has improved the UV transmittance and the decrease in visible light transmittance due to UV irradiation, but the viscosity of the liquidus is as small as 10 ^4.7 dPa · s and the volume resistivity is 10 ^It was as low as ^8.4 Ω · cm.
[0048]
The linear expansion coefficient in the table is obtained by measuring an average linear expansion coefficient in a temperature range of 30 to 380 ° C. with a self-recording differential thermal dilatometer after processing the glass into a cylinder having a diameter of about 3 mm and a length of about 50 mm. is there.
[0049]
The ultraviolet solarization resistance was evaluated as follows. First, a sample was obtained by mirror-polishing both surfaces of a 1 mm thick plate glass. Next, the wavelength of light at which the transmittance of the sample before ultraviolet irradiation showed 80% was measured. Further, after irradiating the sample with ultraviolet light having a main wavelength of 253.7 nm for 60 minutes with a 40 W low-pressure mercury lamp, the transmittance at a wavelength showing a transmittance of 80% is measured again before irradiation, whereby the transmittance by ultraviolet irradiation is measured. Sought to decrease. At this time, the lowering of the transmittance becomes larger as the glass having inferior ultraviolet solarization resistance is reduced. However, it is important that the glass tube for a fluorescent lamp such as a liquid crystal backlight hardly has this reduction.
[0050]
The spectral transmittance in the ultraviolet region was measured by measuring a spectral transmittance at a wavelength of 253.7 nm by preparing a plate glass sample having a thickness of 0.3 mm with both surfaces mirror-polished. The wavelength of 253.7 nm is a mercury emission line. For applications of the present invention, the lower the transmittance at this wavelength, the better.
[0051]
The temperature and viscosity of the liquidus were determined as follows. First, glass crushed to a particle size of about 0.1 mm was placed in a boat-shaped platinum container, held in a temperature gradient furnace for 24 hours, and then taken out. The sample is observed with a microscope to measure the temperature at which the initial phase of the crystal appears (liquidus temperature), and then the viscosity corresponding to the temperature of the initial phase is determined from the relationship between the temperature and viscosity of the glass measured in advance. (Liquidus viscosity) was determined.
[0052]
The volume resistivity was measured at 250 ° C. by a method based on ASTM C-657. For example, in the case of a φ2.6 tube cold cathode fluorescent lamp that is continuously lit at a relatively high voltage of several hundred volts, the temperature in the vicinity of the electrode may exceed 200 ° C. The rate should be 10 ^8.7 Ω · cm or more at 250 ° C.
[0053]
【The invention's effect】
As described above, the tungsten seal glass for a fluorescent lamp of the present invention has a thermal expansion coefficient of 34 to 43 × 10 ⁻⁷ / ° C. suitable for sealing with tungsten metal, and has excellent ultraviolet solarization resistance and ultraviolet light. Since it has shielding properties, devitrification properties, and electrical insulation properties, it is suitable as a glass tube material for fluorescent lamp glass tubes, particularly for fluorescent lamps for liquid crystal display elements that require high quality.

Claims (4)

By mass _{percentage, SiO 2 65~ 72.3%, B} 2 O 3 13 ~25%, Al 2 O 3 2~6%, MgO + CaO + SrO + BaO + ZnO 0.5~5.8%, Li 2 O + Na 2 O + K 2 O 3~ 8%, Fe ₂ O ₃ + CeO ₂ 0.01-4%, Fe ₂ O ₃ 0-0.5% , TiO ₂ + Sb ₂ O ₃ + PbO 0-10%, ZrO ₂ 0-2% Na ₂ O / (Na ₂ O + K ₂ O) ≦ 0.6, tungsten seal glass for fluorescent lamps The tungsten seal glass for a fluorescent lamp according to claim 1, wherein TiO ₂ + Sb ₂ O ₃ + PbO is 0.05 to 10%.   The tungsten seal glass for a fluorescent lamp according to claim 1, wherein the content of BaO is 0.1 to 4%. _{Al 2 O 3 / (SiO 2} + Al 2 O 3) is a fluorescent lamp for a tungsten sealing glass according to claim 1, characterized in that a 0.032 to 0.055.